A gas turbine engine combustor mixes fuel with compressed air for generating combustion gases which are channeled to a turbine which extracts energy therefrom. A typical combustor includes various passages and holes for channeling preselected portions of compressed air from a compressor for performing various functions. A portion of the compressed air is channeled through conventional carburetors for generating fuel-air mixtures which are ignited for generating combustion gases. Another portion of the compressed air is channeled through conventional primary air holes for supporting combustion to ensure that substantially all of the fuel is completely burned. Another portion of the compressed air is channeled into the combustor through dilution air holes for quenching the temperature of the combustion gases and providing acceptable profile and pattern factors, i.e., acceptable temperature distribution, of the combustion gases to the turbine vanes and blades for obtaining acceptable life thereof.
The combustor also typically includes various cooling air holes for channeling additional portions of the compressed air for cooling the dome, carburetor baffle plates, and the combustor liners themselves through, for example, conventional film cooling air nuggets which channel a layer of cooling air along the inner surfaces of the liners for protecting the liners from the hot combustion gases.
A continuing trend in designing gas turbine engine combustors is to reduce combustor length, and length-to-height (L/H) ratio, for reducing engine weight, and increasing engine performance by decreasing the amount of compressor air used for cooling the combustor. However, as combustor length is reduced, it becomes increasingly difficult to obtain adequate penetration of dilution air into, and mixing with, the combustion gases for obtaining acceptable combustion gas exit temperatures. Accordingly, the L/H ratio, which is a primary factor in obtaining acceptable combustor performance, is approaching its smallest limit for conventional combustors.
In order to further reduce overall combustor length, double annular, or double dome combustor designs are being considered since they utilize basically two radially outer and inner combustion zones each having an acceptable L/H ratio while obtaining further decrease in overall combustor length. However, in such double dome combustors, the ability to obtain adequate dilution air penetration and mixing additionally becomes increasingly difficult in view of the relatively short combustor length. Conventional dilution air holes disposed in the combustor liners, are therefore, limited in their ability to obtain acceptable temperature profile and pattern factors.